| 摘要 |
PURPOSE:To make it possible to perform high-speed, automatic control of the amount of projected light, by forming a part, which detects the amount of reflected light from a body, on light receiving surfaces of a photoelectric detector so that the part is separated from a part for detecting a light signal from a pattern, and simultaneously detecting the amount of light in a pattern detecting region and a detected pattern signal. CONSTITUTION:The distribution of scattered light, which is observed at the position of a photodetector 18 of an alignment mark is extended in the direction perpendicular to the extending direction of a pattern. Meanwhile, the scattered light from a material having an irregular shape such as dust spreads uniformly. Light receiving surfaces 18b, 18d, 18f and 18h detect the scattered light caused by the difference in steps in the mark pattern. Light receiving surfaces 18a, 18c, 18e and 18g detect only the scattered light from the dust and the like, which spreads uniformly. Based on the difference, only the signal component, from which the effect of the dust and the like is removed, can be taken out. The amount of the projected light is controlled by said signal at the light receiving surface, which detects non-scattered light. |
